Diagnostic Tests During Pregnancy : An Overview

9 min read

Written by Editorial Team

Editorial Team

Diagnostic Tests During PregnancyDuring the nine months of pregnancy, a woman has to go through many scans and tests to ensure the proper growth of her baby. Yes, we are talking about diagnostic tests during pregnancy. These diagnostics can make her feel as if she has spent most of her time in doctors’ clinics only. But these tests, scans, and regular checkups are essential for a healthy pregnancy. 

They play an important role in identifying, ensuring, and preventing any complications during pregnancy so that you and your baby can remain healthier in the long run. So the question is what do you mean by diagnostic tests and how many tests are needed during the whole period of pregnancy? Here is everything you need to know about the types of diagnostic tests and their benefits during pregnancy. 

In This Article

What Are Diagnostic Tests During Pregnancy?

Diagnostic tests are simple medical tests that help to find any health risk that could affect you or your baby during the nine months of pregnancy. These tests help to diagnose or detect any underlying problem that can potentially affect the health of the mother and the fetus. They can also subclassify them in terms of their severity. According to a study published in NCBI, 3-5% of pregnancies are affected by birth defects (1). Factors like maternal age and hereditary genetic problems may play a role in causing such issues. 

All these can be detected and avoided through prenatal diagnostic tests. Usually, diagnostic test during pregnancy involves ultrasound, blood tests, and urine tests. Most of these tests are capable of diagnosing conditions that can affect fetal health. Getting all these diagnostic tests has become an important part of pregnancy. This not only ensures a healthy pregnancy journey but also helps you avoid or control unwanted complications that can potentially affect your and your baby’s health. 

What Are the Benefits of Diagnostic Tests in Pregnancy?

Here are a few benefits of conducting diagnostic tests during pregnancy

  • Diagnostic tests ensure the early detection of any potential health risk during pregnancy and can help mothers to make well-informed decisions about their health.
  • These tests are effective in detecting abnormalities like certain hereditary or spontaneous genetic disorders.
  • For example, an ultrasound can detect your baby’s growth or any physical abnormality like spina bifida and other structural deformities in the baby.
  • It will also inform you whether you’re having twins or not, and whether your pregnancy is an ectopic pregnancy or a normal one.
  • All these findings can help your doctor in deciding the correct treatment during or after your pregnancy.

Which Diagnostic Tests Are Done During Pregnancy?

Your doctor may perform many tests and scans for a healthy pregnancy. However, there are a few basic mandatory screening tests that help your doctor identify the presence or absence of any kind of health risk that your baby may possess. Depending on the reports, your doctor may decide on prescribing other special tests to further confirm the diagnosis. 

1. Blood-Related Diagnostic Tests

What Are The Benefits Of Diagnostic Tests In Pregnancy_

These tests usually involve a blood sample taken from the pregnant mother. Doctors generally advise most of the blood tests in the first trimester usually during their first visit. But these tests are performed whenever they feel it’s required, most likely in the last trimester.

Some of the blood tests are

1.1 Rh Test

During your first trimester, the doctor will check your blood to confirm the blood group and also to know whether it’s Rh –negative or positive. If it turns out that you are Rh-positive, then an injection known as Anti-D will be given once during the pregnancy and once after childbirth only if your baby is Rh-positive. Anti-D will protect you from developing antibodies that could be dangerous during this pregnancy or in future pregnancies (2).

[Read : RhoGam Shot During Pregnancy]

1.2 Complete Blood Count (CBC)

A CBC test is done to know your hemoglobin range. If it’s less, then the doctor can recommend some iron supplements and can guide you about iron-rich food. CBC also informs about white blood cells and platelet counts during pregnancy. According to studies, in some women, pregnancy can impact the number of white blood cells and platelet counts (3). However, it will come back to normal after the birth of your baby. 

1.3 HIV Test

The HIV test is a must-to-have test for a pregnant woman. If your result is positive for HIV then medications will be given to you to prevent the spread of the virus to your unborn baby. In addition, your doctor can advise you to start thinking about C-sections as they can prevent the spreading of the infection. 

1.4 TSH Test

This test detects the amounts of TSH in the blood. Below-normal levels of TSH indicate hyperthyroidism and is treated with anti-thyroid medications. Thyroid dysfunction has the potential to impact the unborn baby (4). Hence, it is important to get this test done and take appropriate medications and diet to continue with a healthy pregnancy. 

[Read : Impact of Hypo and Hyper Thyroid Pregnant Mother on the Baby]

1.5 T3 and T4 Test

If TSH levels are low, another blood test is performed to measure T3 and T4. Elevated levels of free T4 confirm the diagnosis of hyperthyroidism. 

1.6 Rubella Titer Test

It is done to check the immunity of pregnant women to the rubella virus. Most women are immune to rubella, either because they’ve been vaccinated or had the disease as a child. But if in case you are not immune or your test result shows you are vulnerable to it then it’s very important to avoid anyone who has the infection or has traveled to any such country where the disease is still prevalent. Not being immune to rubella can result in congenital issues in babies, especially it is important not to get exposed to the virus during the initial stages of pregnancy (5).  

[Read : Rubella During Pregnancy]

1.7 Blood Sugar

A blood sugar test is done to check the woman’s sugar levels and also to determine the chances of developing any diabetes in future months of pregnancy. If in case this test shows higher levels, then an immediate change of diet plan or medications is recommended.

1.8 QUAD or Triple Marker Test

The quad test is usually done between 15 to 20 weeks and is also referred to as multiple marker, AFP4, or quadruple test. This test is very useful in the detection of chromosomal abnormalities like trisomy 18 and Down syndrome (6). It can also detect neural tube defects, such as spina bifida.

The positive result of the test will suggest a higher risk and the chance that your baby will have a birth defect and a negative or normal result means that your baby probably doesn’t have a birth defect. But it doesn’t guarantee that you will have a normal baby.

2. Urine-Related Diagnostics Tests

Urine tests

Along with the blood tests your doctor will also recommend you to go for a urine test, which means you have to give them a sample of your urine. Most doctors perform these tests one time during the pregnancy. However, doctors repeat it in case any symptom of urine infection appears at any time during the nine months.

2.1 Urine Tests During First Trimester

The urine test is very important in the first trimester because urine infections if not screened and treated timely can cause serious problems to you and your baby. Simultaneously, it can also detect the presence of traces of blood sugar, or protein.

2.2 Urine Tests During the Third Trimester

Urine tests during the third trimester are important and help in screening any infections and blood sugar levels. 

3. Ultrasound Scans in Pregnancy

Ultrasound Scans in Pregnancy

Ultrasound scans are safe, non-invasive, and a very useful diagnostic tool for screening some birth defects (for example NTD defects). They can also detect an ectopic pregnancy, can assess fetal growth and the risk of Down syndrome. They can also help you with checking fetal heartbeat.  This gives you an estimated date of delivery.

This is especially reliable if in case you have no idea when your last period was. It can inform you if in case you are pregnant with twins. Mostly, doctors perform one in each of the trimesters to check the progress of your fetus.

However, sometimes you might have to do extra scans. Doctors prescribe this if you’re having twins or more. Multiple scans are needed if you have any condition that contributes to a high-risk pregnancy. It is also performed if you’ve had some problems in previous pregnancies.

3.1 Scans in the First Trimester

During the first trimester ultrasound is usually performed between 8 to 13 weeks. This ultrasound confirms the gestational age, position of the placenta, and presence of multiple pregnancies. It also checks the physical growth and development of the fetus. It also helps to know the status of the pregnancy if in case any bleeding is there.

Scans like Nuchal Translucency or NT scans are conducted to identify potential risks for chromosomal disorders like Down syndrome and Edward Syndrome. NT scan which is typically done in week 12 of pregnancy can also help identify certain structural deformities in the baby (7)

3.2 Scans in the Second Trimester

During the second trimester ultrasound is usually performed between 18-20 weeks. This scan detects the growth of your fetus and ensures that all organs like the skull, spine, brain, heart, kidney, and lungs are developing at a normal pace.

Ultrasound in the second trimester, majorly growth scan or TIFFA scan, or an anomaly scan helps to detect neural tube defects, cardiac defects, limb defects, abdominal wall defects, and gastrointestinal malformations like gastroschisis and exomphalos. It also helps identify the position of your placenta.

3.3 Scans in the Third Trimester

During the third trimester ultrasound is often done after 30 weeks, mainly to confirm the position of your fetus and placenta. The third-trimester ultrasounds are performed to keep track of fetal weight gain and to detect if there is any Intra Uterine Growth Restriction or IUGR. 

Close monitoring is needed if you are diagnosed with gestational diabetes, gestational hypertension, or fetal IUGR during the third-trimester growth scan. Ultrasound in the third trimester is a must when the woman is having twins or multiple pregnancies or has a condition that may affect the baby’s growth, such as pre-eclampsia.

4. Other Important Diagnostic Tests During Pregnancy

Other Important Diagnostic Tests During Pregnancy

Some other important diagnostic tests during pregnancy are:

4.1 Glucose Tolerance Test(GTT)

A glucose tolerance test helps to diagnose gestational diabetes in pregnancy. For this test don’t eat or drink anything overnight.  The technician measures the level of sugar in your blood when you’ve been fasting. They will take your first blood sample. Then they will ask you to drink 75g of glucose drink. 

A glucose tolerance test is usually performed in the third trimester of pregnancy, but research studies claim that there is a possibility of developing Gestational Diabetes Mellitus (GDM) even during the early weeks of pregnancy. Getting the test done can help avoid unnecessary maternal and fetal complications (8).

The technician tests the blood one hour after drinking the glucose. If you have high blood sugar levels on a glucose tolerance test, you have gestational diabetes. This makes your pregnancy a high-risk pregnancy.

4.2 Non-Stress Test (NST)

Doctors perform NST weekly in your third trimester. Doctors prefer to do it throughout the last month of pregnancy if it is coming under high-risk pregnancies. This test monitors the baby’s heart rate and their movements. The technician straps the fetal monitor across the mother’s abdomen for monitoring (9)

[Read : Non-Stress Test During Pregnancy]

4.3 Contraction Stress Test

Doctors perform CST in the third trimester for high-risk pregnancies. Here a fetal monitor measures the baby’s heart rate in response to contractions stimulated by oxytocin. This test helps to predict how well the baby will cope with the stress of labor (10).

Apart from all these diagnostic tests during pregnancy regular checkups are very important. A routine check-up in combination with diagnostic tests can help to keep you and your baby healthy.


1. Are Diagnostic Tests Mandatory During Pregnancy?

Diagnostic tests during pregnancy or prenatal diagnostic tests can help identify possible risks and complications that can hinder the development of the baby. Early detection and prompt treatment can help avoid them and allow you to have a smooth pregnancy. 

2. What Happens if I Ignore Hypothyroidism During Pregnancy?

Ignored thyroid dysfunction during pregnancy can result in low birth weight, fetal congenital abnormalities, and poor cognitive development in babies. Ignored thyroid can also cause the baby to inherit thyroid disorders, and miscarriages in early pregnancy. 


  1. Prenatal Diagnosis – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548328/]
  2. Pregnancy and birth: What is the benefit of determining the Rh factor before birth? – [https://www.ncbi.nlm.nih.gov/books/NBK546246/]
  3. Establishment of reference intervals for complete blood count parameters during normal pregnancy in Beijing – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6816986/]
  4. Thyroid physiology and common diseases in pregnancy: review of literature – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3530964/]
  5. The status of rubella IgG antibody titer between antenatal and postnatal among pregnant non-immune to rubella – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7899702/]
  6. Performance of Serum Quad Test in Screening for Fetal Down Syndrome in a Large-Scale Unselected Population in a Developing Country – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10114521/]
  7. The Associations of Nuchal Translucency and Fetal Abnormalities; Significance and Implications – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681077/]
  8. Need for testing glucose tolerance in the early weeks of pregnancy – [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4743382/]
  9. Prenatal Nonstress Test – [https://www.ncbi.nlm.nih.gov/books/NBK537123/]
  10. Contraction stress test for antepartum fetal evaluation – [https://pubmed.ncbi.nlm.nih.gov/1121373/]
Editorial Team,

With a rich experience in pregnancy and parenting, our team of experts create insightful, well-curated, and easy-to-read content for our to-be-parents and parents at all stages of parenting.Read more.

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